1. Field of the Invention
The invention relates to a single-web loom for weaving loop velvet fabric, and it also relates to a method of weaving such a velvet fabric. Such a velvet fabric may present, in a single row parallel to the weft direction, both loops and pile.
2. Brief description of the Related Art
So-called “loop velvet” looms are single-web looms in which the warp comprises both backing yarns and yarns for forming loops or pile. Such looms present superposed sheds. The bottom shed enables weft to be inserted by rapiers, while higher sheds enable respective rods to be inserted around which some of the warp yarns then form loops. The rods are driven by a device situated on one side of the fabric, which device acts during one pick to insert a rod that it withdrew from the fabric during an earlier pick. Different rods moved by a device situated on one side of the loom can carry respective blades at one end, such blades serving to cut the loops when the corresponding rod is withdrawn, thereby forming two threads of pile. By alternating rods both with and without blades, it is possible to produce a fabric that presents both loops and pile.
In the field of furnishing, there is a strong demand for fabric presenting simultaneously backing effects, loops, and pile. Loop velvet looms make it possible to combine loops and pile of different heights in a single row parallel to the weft direction.
A first method of achieving this objective is shown diagrammatically in FIGS. 1 and 2. It requires four picks A, B, C, and D. Two warp yarns 11 and 12 form the backing of the fabric in association with weft yarns 2. During pick A, another warp 13 forms a loop about a rod 31, prior to being incorporated in the backing of the fabric until the fourth pick D. A fourth warp yarn 14 forms a loop around the rod 31 and around a rod 32 that carries a blade, this second rod being inserted during the third pick C over the backing of the fabric. By using an appropriate backing weave, such as “4/4” or “2/2”, and by inserting no weft yarns during the second and third picks B and C, the beat-up by the comb following the insertion of the second rod 32 during pick C places the second rod 32 above the first rod 31. After the first and second rods 31 and 32 have been withdrawn, a row is formed comprising pile P made using the yarn 14 and extending away from a midplane Π of the backing of the fabric over a height that is greater than the height of the loop BO. That method is not very productive since it requires four loom picks to produce one row of loops and pile.
Another method consists in inserting a “double iron” member comprising two superposed rods, one for forming a loop and the other, superposed above the first, for forming pile. It is then necessary to form three sheds in order to insert simultaneously backing weft and two rods, thus making it necessary to use shed-forming means capable of placing warp yarns in four different positions. It is then necessary to use four-position Jacquard mechanisms, as disclosed for example in EP-A-0 665 312, making use of a relatively complex and bulky tackle system. The cost price and the complexity of such mechanisms are such that they are little used in practice.
U.S. Pat. No. 5,522,435 makes provision for obtaining four positions from a three-position Jacquard machine combined with a moving support. If such equipment is used with rods, then during the rod extraction pick, the warp yarns can be placed beneath or above the weft, and also between the rods. During the rod insertion pick, the yarns can be placed beneath or above the pile rod, or above the weft. Such an approach does not make it possible to place a pile or loop yarn beneath the weft in order to create a backing effect.
In another approach, it is possible to combine two three-position Jacquard devices. The shed of the first device is adjusted so as to be capable of controlling the loop yarns, while the shed on the second device is adjusted so as to be capable of controlling the pile yarns. That solution reduces options for weaving since the warp yarns for the loops cannot be used to form pile, and vice versa.
Thus, weaving options with known devices on a loop velvet loom are limited both in terms of flexibility and in terms of the productivity that is obtained.